Gay rights advocates hope that points to a quick ruling in their favor.

Gwynne Skinner, associate professor of law at Willamette University in Salem, says U.S. District Judge Michael McShane might rule quickly. Or he might not. Either way, Skinner says don't try to guess how the judge will rule based on how he acts in court on Wednesday.

"It is very difficult to predict a judge's decision simply based on the questions because often times the judge is just trying to play devil's advocate or test different thoughts or different arguments."

Skinner says if the judge rules in favor of the plaintiffs, an appeal of that decision is unlikely. That's because the only parties with the ability to appeal are already on the side of overturning the law.

Gay rights advocates are hoping for a swift ruling. They want to avoid a potentially costly ballot measure campaign to overturn the law.